1. Field of the Invention
The present invention relates to a dielectric waveguide antenna.
2. Description of the Related Art
Recently, research into a transmission and reception system using a high frequency of a millimeter wave band has been actively conducted.
Particularly, the huge demand for a short-range wireless communication system using a broadband frequency of a 60 GHz band and a car radar system using a frequency of a 77 GHz band is expected.
In the transmission and reception system using a frequency of the millimeter wave band, the demand for development of a product in a system-on-package form has been increased in order to reduce loss generated during coupling of components, reduce a production cost through a single process, and miniaturize a product.
Generally, a size of an antenna is in inverse proportion to an operation frequency thereof, and a length thereof may be miniaturized to several millimeters in a millimeter wave band of 30 GHz or more.
Due to the miniaturization of an antenna size and the development of a multi-layer structure process such as a low temperature co-fired ceramic (LTCC) process, liquid crystal polymer (LCP) process, and the like, the transmission and reception system using the frequency of the millimeter wave band may be produced as the product in the system-on-package form.
A patch antenna having a planar structure has been mainly used in a stacking substrate environment such as the LTCC process and the LCT process. However, in the patch antenna, a horn antenna having a metal rectangular waveguide shape has been mainly used.
The horn antenna has high efficiency and broadband characteristics; however, it requires three-dimensional processing of a metal, has a large volume, and also has defects in a micro-snip or a strip line pit used in a general multi-layer substrate structure.
In order to solve these problems, an aperture antenna having a stacking structure and formed by implementing a rectangular waveguide in an inner portion of a stacking substrate using a via hole and modifying the horn antenna has been developed. However, in the aperture antenna of a stacking substrate environment, a problem in radiation characteristics may be generated.
Meanwhile, when a dielectric material is filled in an inner portion of the waveguide, a reflection coefficient between air and a waveguide antenna is increased, such that the radiation characteristics of the antenna are deteriorated.
The reason is that while radiation resistance on an aperture surface is not largely changed, a system impedance of the waveguide antenna is decreased due to increase in an electric constant.
Generally, the dielectric material used in a dielectric waveguide antenna has a dielectric constant of 6. However, a case of using a dielectric material having a high dielectric constant of 7 to 9 in order to reduce a size of the entire system and increase a Q value in a product such as a filter, etc., has been increased. In this case, a mismatch in the radiation resistance on the aperture surface is further increased.
As such, when the dielectric waveguide antenna according to the prior art is directly applied to the stacking substrate environment, reflection in an aperture of the dielectric waveguide antenna is increased due to the mismatch in the reflection resistance between the air and the dielectric waveguide antenna, such that antenna characteristics are deteriorated.